This disclosure relates to the field of apparatus disposed below the surface of the earth operated by pneumatic pressure. More particularly, the disclosure relates to pneumatically operated apparatus that use repeated increases and decreases in pneumatic pressure to operate.
U.S. Pat. No. 8,991,504 issued to Hansen discloses a wellbore pump for use in wellbores drilled through fluid producing formations in the subsurface. The disclosed pump is operated by repeatedly applying pneumatic pressure to a pump chamber to displace fluid in the pump chamber into a conduit extending from the wellbore pump to the surface. The pneumatic pressure is then bled off to enable fluid from a fluid producing formation to enter the wellbore and the pump chamber. Pump operation requires repeated pneumatic pressurization and bleeding of the pneumatic pressure.
A substantial amount of energy is required to pressurize a power fluid conduit extending from the surface to the wellbore pump that supplies the pneumatic pressure to operate the foregoing pump. The amount of energy required to pressurize the power fluid conduit is related to the length of the power fluid conduit. For wellbore pumps disposed at great depth in a wellbore, therefore, the energy required to operate such a pneumatically powered wellbore can be prohibitively expensive.